pg tp-class21-humidity
TRANSCRIPT
Physical GeographyClass 21: Humidity
A measure of how much water vapor is in the air
What is humidity?
What is the source(s) of water vapor?
20%
60%
0%
0%
0%
0%
20%
0% 1. Transpiration2. Evaporation3. Deposition4. Sublimation5. Condensation6. 1, 2 and 37. 2, 3 and 58. 1, 2 and 4
What happens if wind increases?
0%
20%
20%
40%
20% 1. Condensation increases2. Evaporation increases3. Condensation + evaporation
increase4. Evaporation decreases5. Both condensation and evaporation
decrease
Air with high levels of water vapor:
60%
0%
20%
20%
0% 1. Will lead to high rates of evaporation
2. Will lead to low rates of evaporation3. May lead to condensation4. 1 and 25. 2 and 3
Actual amount of water vapor◦ Absolute Humidity◦ Specific Humidity◦ Vapor Pressure◦ Dew Point
Different ways to express humidity
Mass of water vapor/volume of air
Units: grams/cubic meter
Maximum potential absolute humidity related to temperature
Temperature increase = increase in potential maximum
Absolute Humidity
Mass of water vapor per mass of air
Grams of water vapor/kilograms of air
Specific Humidity
The portion of air pressure that comes from water vapor
Units: same as air pressure (millibars)
Saturation vapor pressure = maximum possible
Above saturation condensation
Vapor Pressure
Sat. V.P increases with temp.
Temperature and Relative Humidity
As water vapor in air cools, what phase change is likely to occur?
1. Evaporation2. Transpiration3. Condensation
What are two ways that maximum water vapor can be reached?
1. Add more moisture and lower temperature
2. Remove water vapor and lower temperature
3. Add more moisture and raise temp4. Remove water vapor and raise
temp
If the absolute humidity stays same, what will happen as temp increases?
1. Relative humidity will increase2. Relative humidity will stay same3. Relative humidity will decrease
Which has the potential to contain more water vapor?
1. Warm air2. Cold air
As air cools, maximum water vapor can be reached.
Dew Pt temperature = temp. at which this occurs
100% Relative Humidity or Saturation
Dew Point/CondensationTemperature
Dew point is a way of measuring:
1. The actual amount of water vapor in the air
2. The relative humidity
A high dew point means
1. A high amount of water vapor2. A low amount of water vapor3. A high relative humidity4. A low relative humidity
How can saturation be reached?
0%
0%
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0% 1. By evaporation of more water2. By condensation of more water3. By lowering temperature4. By raising temperature5. 1 and 36. 2 and 47. 1 and 48. 2 and 3
Hot and dry vs. hot and humid (heat index)
Cold and humid vs. cold and dry
Wind chill
Human Comfort and Humidity